VOICE. 



fhakos, or rapid changes of intervals in finging, however 

 fmall may be the difference of tone. 



Hence, as the depth of the tone of an hautboi? is anfwer- 

 able to the length of the inllrumcnt ; the longelt fibres of 

 the wood, whofe vibrations make the refonance, making 

 always the floweft vibrations, and confequcntly the deepeft 

 tone, it may appear probable, that the concavity of the 

 mouth, by its lengthening for grave tones, and fhortening 

 for acute ones, might lerve very well for the production of 

 the divers tones ; but M. Dodart obferves, that in the ilop 

 of the organ called the human voice, the longeft pipe is fix 

 inches ; and yet, with all that length, it does not make any 

 difference of tone ; but the tone of the pipe is precifely that 

 of the plug : whereas tlie concavity of the mouth of a man 

 of the graved voice, not being above fii: inches deep, it is 

 evident that cannot modify, vary, and give the tone. 



It is the glottis, then, that forms the tone, as well as the 

 found ; and the manner of forming the various tones is by 

 Tarying its aperture : a piece of mechanifm too admirable 

 not to be here particularly inquired into. 



The human glottis, then, reprefented in Plate XXIV. 

 Mifcellany, fig. 9. is only capable of one proper motion ; 

 viz. that of an approach of its hps A D B, and A D B. 

 Accordingly, the dotted Unes A E B, A F B, A G B, 

 exhibit three different degrees of approach. Thefe different 

 apertures of the glottis anatomifts ufually attribute to the 

 aAion of the mufcles of the larynx ; but M. Dodart fficws, 

 from their pofition, direction, &c. that they have other 

 ufes ; and that the opening and fhutting of the glottis is 

 effeded by other means, wz. by two tendinous corda, or 

 firings, inclofed in the two lips of that aperture. 



In effeft, each of the two femicircular membranes, whofe 

 interftice forms the glottis, is doubled back upon itfelf ; 

 and within each duplicature there is a corcI, or firing, which 

 is fattened at one end of the fore-part of the larynx, and to 

 the hind-p<urt at the other. It is true, they appear more 

 like ligaments than mufcles, as confifling of white and mem- 

 branous fibres, not of red and flefliy ones ; but the vaft 

 number of minute changes in this aperture neceffary to form 

 the vaft. variety of tones, make an extraordinary kind of 

 mufcle, by whofe contraftion they fhould be effeAed, ab- 

 folutely neceffary. Common flefhy fibres, in which the 

 blood is received in large quantity, had been infinitely loo 

 coarfe for fuch delicate motions. 



Thefe ftrnigs, which, in their ftate of relaxation, make 

 each a little arc of an ellipfis, as they contrail more and 

 more, become longer, but lefs and Icfs curve ; and at lalt, 

 with the greateft, contraflion they are capable of, they de- 

 generate into two right lines, applied clofe to each other ; 

 io clofe, and fo firm, that an atom of air cannot efcape out 

 of the lungs, how full foever they may be, and how great 

 an effort foever all the mufcles of the lower venter may make 

 againft the diaphragm, and, by the diaphragm, againil tUefe 

 two little mufcles. 



The different apertures of the lips of the glottis, then, 

 produce all the diftiTcnt tones in the fcveral vocal parts of 

 mufic ; "Ufz,. bafe, barilono, tenor, eounlcr-tcnor, and trebles ; 

 and the manner is thus : 



The voice, we have fliewn, can only be formed by the 

 glottis ; but the tones of the voice arc modifications of the 

 voice ; and thefe can only be produced by the modifications 

 of the glottis. Now the glottis is only capable of one modi- 

 fication, which is tlie mutual appro.ich, or recefs of its lips : 

 H is this, therefore, that produces the different tones. Now 

 that modification includes two circumilances ; the firft and 

 principal is, that the lips are ftrotched more and moic, from 



Vol. XXXVII. 



the lowed tone to the highed ; the fecond is, that the more 

 they are dretched, the nearer they approach. 



From the fird it follows, that their vibrations will be fo 

 much the quicker, as they come nearer their highed tone ; 

 and that the voice will be jud, when the two lips are equally 

 dretched ; and falfe, when they are unequally ; which agree* 

 perfeftly well with the nature of dringedinilruments. 



From the fecond it follows, that the higher the tones are, 

 the nearer will they approach to each other ; which agrees 

 perfeftly well with wind-indruments governed by reeds or 

 pluffs. 



The decrees of tenfion of the lips are the fird and prin- 

 cipal caufe of tones ; but their differences are infcnfible. 

 The degrees of approach are only confequences of that ten- 

 fion ; but their differences are more eafily afligned. ' 



To give a precife idea of the thing, therefore, we had 

 bed keep to that, and fay, that this modification confids in 

 a tenfion, from whence refults a very numerous fubdivifion 

 of a very fmall interval : which yet, fmall as it is, is capable, 

 phyfically fpeaking, of being fubdivided infinitely. 



The doftrine is confirmed from the different apertures 

 found in diffefting perfons of different ages, of both fexes. 

 The aperture is lefs, and the exterior canal always diallower, 

 in the fex and ages fitted to fing treble. Add, that the 

 reed of a hautbois, feparated from the body of the inftru- 

 ment, being a little preifed between the lips, will yield a 

 tone fomewhat higher than its natural one ; and if prcffed 

 dill more, will yield another dill higher : and thus an able 

 mufician may run fucceflively through all the tones and femi- 

 tones of an oftave. They are different apertures, then, that 

 produce, ov, at lead, that accompany, different tones, both 

 in natural wind-inffruments and artificial ones ; and the di- 

 minution of the aperture raifes the tones both of the glottis, 

 and the reed. 



The reafon why leffening the aperture heightens tlie tone 

 is, that the wind pafles througli it with the greater velocity j 

 and from the fame cauie li io, that if any reed or plug, of 

 an indrument, be too weakly blown, its tone will be lower 

 than ordinary. 



Indeed the contradions and dilatations of the glottis muft 

 be infinitely delicate : by an exaft calculation of the iiv 

 genious autlior above-mentioned, it appears, that to per- 

 form all the tones and femitones of a common voice, which 

 is computed to reach twelve tones ; to perform all the par- 

 ticles and fubdivifions of thofe tones into commas, and other 

 minuter, though dill fenfible parts ; to perform all tht 

 diakes, or the difkiLnces in a tone when founded more or 

 lefs drong, withoi.l changing the tone ; the little diameter 

 of the glottis, which does not exceed one-tenth of an inch, 

 but wiiich varies within that extent at every change, muft 

 be aftually divided into 9632 parts ; which parts arc yet 

 very unequal, and, therefore, many of them much lefs than 

 the .,r^v, .nth part of an inch: a delicacy fcarcely to be 

 matched by any thing but a good ear, which has fo juft a 

 fenfe of found, as, naked, to perceive diftcrencca in all 

 thefe tones ; even thofe whofe origin is much lefs than the 

 963200111 part of an inch. 



With refpeA to tlje organ of voice, Rouffcaii. in 176^, 

 when he publidicd his Mufical DiAionarv, was able to find 

 no more fatisfaftory account than that which he has given 

 from Duclos and Dodart ; nor have we fincc been able to 

 find that any further progrefs has been made into this my(- 

 tery of nature. We have converfed with the late I>r. 

 William Hunter, .ind his brother, the great anatomid, Mr. 

 .lohn Hunter, on the fubjed, who agreed that there was no 

 work of nature more fubtile and iiiexplicible than lj:e form-. 

 3 I M0<\ 



